Heretofore, high frequency heat seals for sealing a glass container by attaching a cap inside of which is covered with a sealing material (e.g., a material in which an adhesive layer of a thermoplastic synthetic resin film is laminated to the under surface of aluminum foil) to the top of the opening of a glass container, and high-frequency heating the cap for welding of the synthetic resin film of the sealing material to the top of the opening of the glass container or heat seals for sealing a glass container by disposing a sealing material (a material having an adhesive layer of a thermoplastic synthetic resin film on the rear surface) to the opening of a glass container, and heating the sealing material from the front surface side thereof for welding of the synthetic resin film have been known.
The following Patent Documents 1 to 5 disclose sealing methods for increasing sealing strength or securing sealing strength also to weathered glass containers when such sealing is performed.
Patent Document 1 discloses coating the top of the opening of glass containers with saccharides. Patent Document 2 discloses coating the top of the opening of glass containers with polyvalent metal salts and saccharides. Patent Document 3 discloses coating the top of the opening of glass containers with polyvalent metal salts. Patent Document 4 discloses hot end coating the top of the opening of glass containers, coating the same with a silicon oxide or silicate, and further coating the same with a silane coupling agent. Patent Document 5 discloses coating the top of the opening of glass containers with pectin.    Patent-Document 1: Japanese Unexamined Patent Application Publication No. 2003-160161    Patent-Document 2: Japanese Unexamined Patent Application Publication No. 2003-226350    Patent-Document 3: Patent-Document 1: Japanese Unexamined Patent Application Publication No. 2003-226353    Patent Document 4: Patent-Document 1: Japanese Unexamined Patent Application Publication No. 2005-177542    Patent Document 5: Japanese Unexamined Patent Application Publication No. 2006-298432
All the above-described former techniques increase seal strength or secure sufficient seal strength even when glass is weathered, but have been insufficient from the viewpoint of water resistance of sealing.